Directional lifting in v-dmc

A method of decoding a bitstream of encoded mesh data, the method comprising:

• receiving, in the bitstream of encoded mesh data, a first syntax element indicating a base value;
• receiving, in the bitstream of encoded mesh data, a second syntax element indicating an exponent value;
• determining a delta scale value based on the base value and the exponent value;
• performing an inverse directional lifting transform to determine a displacement vector for a target vertex of a base mesh based on one or more of a first scale value, a second scale value, or a third scale value determined based on the delta scale value;
• deforming the base mesh based on the displacement vector to determine a deformed base mesh;
• and
• determining a decoded mesh based on the deformed base mesh.

A non-transitory computer-readable medium storing instructions that, when executed by processing circuitry, cause the processing circuitry to:

• receive, in a bitstream of encoded mesh data, a first syntax element indicating a base value;
• receive, in the bitstream of encoded mesh data, a second syntax element indicating an exponent value;
• determine a delta scale value based on the base value and the exponent value;
• perform an inverse directional lifting transform to determine a displacement vector for a target vertex of a base mesh based on one or more of a first scale value, a second scale value, or a third scale value determined based on the delta scale value;
• deform the base mesh based on the displacement vector to determine a deformed base mesh;
• and
• determine a decoded mesh based on the deformed base mesh.

A device for generating a bitstream of encoded mesh data, the device comprising:

• one or more memory units;
• one or more processing units implemented in circuitry, coupled to the one or more memory units, and configured to:
• perform a plurality of forward directional lifting transforms on a displacement vector for a target vertex of a base mesh using different scale values to determine a first scale value, a second scale value, and a third scale value;
• determine a delta scale value based on the first scale value, the second scale value, and the third scale value;
• determine a base value based on the delta scale value;
• determine an exponent value based on the delta scale value;
• perform a forward directional lifting transform on the displacement vector for the target vertex of the base mesh based on one or more of the first scale value, the second scale value, or the third scale value to determine one or more transform coefficients;
• encode the one or more transform coefficients to determine encoded transform coefficients;
• and
• generate the bitstream of encoded mesh data, the bitstream comprising a first syntax element indicating the base value, a second syntax element indicating the exponent value, and additionally syntax elements indicating the encoded transform coefficients.